Subsea wellbores can be drilled using a dedicated drilling vessel or drilling rig. The drilling vessel can be used to drill a series of successively smaller wellbores and install one or more conductors in the wellbores in order to maintain hole integrity and establish well control.
A large open water hole may be drilled or jetted for running a length of conductor connected to a low pressure wellhead housing. Subsequently, a second smaller hole may be drilled within the first into which a length of surface casing connected to a high pressure wellhead housing may be run. These two casing strings can be suspended from wellheads located at the seabed. This method of drilling can result in large quantities of drill cuttings and drilling fluids being deposited into the environment. This method of drilling can be vulnerable to shallow gas encounters and can depend on equipment such as a rotary table, a top drive, a derrick, etc., which may be only available on a dedicated drilling vessel. Once the high pressure wellhead is installed on the seabed the dedicated drilling vessel may run and install the BOP stack, which may be followed by the installation of a marine riser. From this point forward a full well control package may be available, which can respond to any wellbore influx. The use of a dedicated drilling vessel or drilling rig can be very costly and time intensive.
A method and associated apparatus for setting one or more conductor casing strings is described in WO01/65050 (Strand, H.). The Strand apparatus and method requires the use of a suction substructure, which allows the installation of conductor casing by means of piling.
U.S. Pat. No. 4,830,541 describes an apparatus, which is equipped with a venture suction device and a central opening for receiving a well conductor pipe.